A device of the type described above is previously known from the Swedish Patent specification No. 223 476. The flattened end portion with recesses which can be considered as constituting opposingly directed hooking elements in sequence with each other is formed by considerable forgoing of one end of a bar material, the main portion of which forms the shank. The shank end portion is forged to provide a shape substantially that of an "S". The take-up chain's end link is fitted to a hole in the end portion in the junction area between shank and end portion. The junction area is forged out to a substantial height for withstanding the bending stresses occurring, and because the bore reduces strength in the highly stressed area. Due to the height which is forged, the end portion is laterally weak which easily causes the device to collapse with heavy stresses. The locking chain is attached to the other end of the shank in a corresponding way, although the stresses do not cause any risk of collapse or rupture. On the other hand, such a type of connection results in substantial costs, since a bore must be arranged through the bar material and the link connecting to the bore must be clipped up and threaded through the bore for being finally welded together.
Due to the end portion provided with recesses or hook elements having to be forged out to a substantial height, the problem occurs that the end portion must be given a shape substantially that of an "S". This signifies that with normal link sizes it is not simple to insert the end portion of the device through the chain link in question. In this connection it should be noted that in producing the devices in question the initial material is uniformly thick bar stock for reasons of strength and cost, this stock being forged to desired shape whereafter measures are taken to allow attachment of take-up chain with associated hook and locking chain with associated hook.
The known device is thus burdened with a plurality of disadvantages relating to form/strength, use and production costs.